Electric material and process for making same



Patented Dec. 3, 1929 UNITED STATES PATENT OFFICE JOHN DE GIOVANNI, OI BROOKLYN, NEW YORK ASSIGNOR TO POLYMET MANUFAC- TUBING CORPORATION, NEW YORK, N. Y., A CORPORATION OF NEW YORK No Drawing.

' larly by the wide and general use of radio receiving apparatus has created a necessity for a resistance material which will afford relatively high resistances without becoming too hot in operation. The heat developed in the ordinary resistance as now employed in the form of copper or German silver wire and the like makes necessary special provision for effective heat radiation and even where such provision is made, the heated resistance element makes operation of the particular electrical apparatus dangerous as well as ineflicient and uneconomical and very often results in the necessity of replacing parts or discarding the unit.

Another disadvantage of the resistances now employed is that where coils of wire have to be used to afford a high resistance, a large length of wire has to be used to give the desired amount of resistance, thus involving a comparatively high cost.

It is the object of this invention to provi ie a conducting material which shallgive effective resistance with efiiciency in operation and comparatively little heatin and furg thermore be. economical in use, both as to the space occupied and the amount of material required to produce a given ohmic quantity.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

In accomplishing these and other objects, I have availed myself of the well known'fac't that nearly all salts of metals are reduced more or less to a metallic state by the action of ultraviolet light. Silver salts have been found to be more sensitive than others in this connection. Thus silver bromidewhen subjected to ultra violet light will readily be reduced so as to leave a deposit of metallic silver. Briefly described, I provide a resistance material wherein a cheap mounting of ELECTRIC MATERIAL AND IPRQCESS FOR MAKING SAME Application filed January 27, 1927. Serial No. 164,128.

insulating material is employed as the body portion or base on which a metallic coating is formed which provides a thin conducting surface that affords the resistance to the electric current.

The following is an example of the carrying-out of my invention: I make a solution of a silver salt such as silver nitrate and a solution of potassium bromide. The silver nitrate solution is then mix-ed thoroughly with a binder preferably in the form of an emulsion of some adhesive sub stance, such for example as gelatin. A sufficient quantity of the potassium bromide is then added to reduce the silver to silver bromide. There results a massof' silver bromide particles suspended in the gelatin emulsion. The base or mounting is then dipped in the'solution and held therein so as to become impregnated therewith. It is then dried in any suitable manner under exposure of ordinary daylight, which reduces the bromide to some extent to metallic silver, The impregnated mounting is then immersed in an organic reducer such as paramido-phenol and sodium sulphiteso as to completely reduce the bromide to the metallic silver. The material is then washed and dried.

For the mounting I preferably employ a cheap nonconducting material such as blotting paper which is sufiiciently porous so as to become easily impregnated. There results from the treatment of this blotting paper as hereinbefore described, a flat material which is flexible and can be rolled up and cut as desired, having a fine coating of silver.

It will be seen that the material made in accordance with the foregoing description comprises a comparatively thick, non-con ducting body portion on which is spread a very thin, metallic film of large superficial area which serves as the conductor for the current. I have found that this material material, the ohmic resistance of which has been determined, is connected in series with a copper mm of the same resistance so that the same current flows through both under the same E. M, F., the Wire will get much hotter than the material, the latter remaining comparatively cool.

Other mounting materials and other metal coatings may of course be employed. Where a sufficiently porous material cannot be used, the impregnation may be effected under pressure.

The binder solution, like the mounting, should also be preferably of an adhesive substance which is non-conducting.

The invention has been described particularly with reference to the practical application of the material for electrical resistances.

It will of course be understood that it may serve other purposes for which electrical conducting materials are usually employed.

In addition to making up this material in flat strips as Will result from the particular illustration herein described, I contemplate making the material up also in the form of Wire. For this purpose, the ordinary enamelled or cotton covered wire may be employed. The outside covering of the wire is used for the backing and is impregnated in the same manner as above described. The copper Wire itself is employed only to provide a core or base to give body to the material and connection'is made to the outside covering where electrical contact is had by means of the thin metallic layer.

It will thus be seen that there is provided an article of manufacture and process in which the several objects of this invention are achieved, and which are well adapted to meet the conditions of practical use.

Having thus described my invention, I claim as new and desire to secure by Letters Patent v 1. The herein described process for making materials of the character described consisting 1n impregnating a conducting member.

having a central metallic Wire and a covering of insulating material with a solution of a silver salt and reducing said salt.

2. The herein described process for making materials of the character described consisting in mixing an emulsion of silver nitrate with a solution of potassium bromide, of dipping a conductor cable having an outer cover of porous non-conducting material into said mixture until said cover is impregnated, of drying the resulting material in daylight, of then impregnating the said material in paramido phenol and sodium sulphite and of washing and drying the resulting product.

In testimony whereof I affix my signature.

'JOHN DE GIOVANNI. 

